The present invention relates to precision-type, single-seed drilling planters, which are adapted to deposit seeds one-by-one in the ground at regular intervals along sowing rows.
In the cultivation of maize, sugar beets, soya, horticultural-type vegetables and the like, single seed planters are well known for sowing or depositing either peeled or unpeeled, bare or coated seeds at a regular spacing. Precision-type single-seed planters have a number of advantages as compared with universal-type ones. These advantages include a reduction in or even the elimination of downtimes required to subsequently carry out a thinning out of the plants, a simplification in the tilling and harvesting operations, and a saving in the quantity of seeds used.
Precision-type single-seed planters can essentially be divided into two categories based on the distribution system that they implement, i.e. mechanical or pneumatic.
The present invention relates to precision-type single-seed planters falling into the pneumatic-type category, in which the withdrawal of the seeds from the loading container, their separation and their distribution one-by-one are performed by a rotating perforated disk having one or more concentric series of perforations. A suction blower acts on one side of the disk to create a vacuum through the perforations of the disk and thereby keep the seeds adhering to the disk until the seeds reach a discharge zone. A mechanical separator on the other side of the disk is provided to select, one by one, the seeds to be adhered to the disk by causing excess seeds to fall back into a seed container.
In single-seed planters of the known type, in which the perforations of the disk are generally circular, it is rather difficult to ensure that only a single seed adheres to the disk at each perforation of the disk, particularly in those cases in which the seeds have no regular shape and/or have differing sizes. It is therefore general practice to use disks with quite large perforations so as to ensure that at least one seed is in all cases captured for distribution. However, by increasing the size of the individual perforations so as to enable even the largest seeds in the lot to be held by sufficient suction in the perforations, a further problem is created in that smaller seeds then have the opportunity of passing through the perforations, or else in that many smaller seeds may get stuck in the perforations, thereby obstructing them. It is therefore quite difficult to succeed in separating the seeds in a manner in which only a single seed is actually held under suction at each perforation. Further, the seeds that become stuck in the perforations may ultimately be broken up by the separator when the latter interacts with the perforated disk.
It therefore ensues that precision-type single-seed planters have to be provided with several sets of perforated disks having perforations drilled to different diameters. The disks must therefore be changed quite often according to the average size and shape of the seeds to be planted, so as to reduce the extent of the above-described drawbacks.
Furthermore, the separators must be positioned and adjusted in such a way as to ensure that a single seed remains at each perforation. However, in the precision-type single-seed planters of the known type this is not possible when the seeds have irregular shapes, since any adjustment enabling two smaller seeds to be effectively separated will quite often prove inadequate in keeping a larger seed adhering to the disk, and so the larger seeds will often fall back into the seed container and create a void in the sowing sequence. In the opposite case, any adjustment of the selector that enables large or ill-positioned seeds to be kept adhering to the disk may enable several smaller seeds to pass through a perforation, thereby giving rise to an irregular seed deposition pattern.
Italian patent specification no. 1.145.917 filed by F. Walter & H. Wintersteiger KG describes a precision-type single-seed drilling machine of the pneumatic type, in which the seed drilling disk is formed by two parts, namely by a disk-type body member connected to the suction fan and a thin disk-like plate adhering against the surface of the body member and facing the supply of seeds. The disk-type body member is fixed and is provided with a guide slot extending from the center to the periphery of the body member so as to follow the ejection path of the seeds. The disk-like plate is rotatable and is provided with a plurality of radial slots extending from the central portion to the periphery of the disk. This particular type of construction enables a slower speed to be implemented at which the seeds are extracted from the container, and therefore facilitates a more effective capturing of the seeds by the disk. This occurs owing to the fact that the slots are arranged in a radial pattern and extend from the central portion of the disk. However, in order to enable the seeds to adhere at a small central portion of the disk, only a limited number of slots can be provided. It therefore ensues that, with the distribution of a small number of seeds for each rotation of the disk, it is necessary to work at a very slow forward-moving speed on the field, otherwise there would be no effective or even acceptable sowing action since the seeds would necessarily be subjected to an excessively high centrifugal force.
Although such a system operates quite effectively when used with seeds having a roundish shape, it is clearly less effective when it comes to individually distributing single seeds having irregular shapes, e.g. tapered or pointed, or having differing sizes. Furthermore, this system has a rather complicated structure as it practically requires a two part disk body, each of the parts having to be provided with a number of special slots.
It should further be stressed that the seeds contact both parts of the disk and are subjected to a rolling action which, on the one hand, may promote the separation of the seeds but, on the other side, will cause the seeds to become damaged owing to the considerable friction which arises between the seeds and the surfaces of both parts of the disk along a considerable length of travel of the seeds.
European patent application no. 0.338.883 filed by ATELIERS RIBOULEAU describes a precision-type single-seed drilling machine of the pneumatic type, in which the distribution disk is provided with circular, equally spaced perforations arranged in one or two circular patterns near the outer edge of the disk.
The main feature of this machine resides in the suction device which has an inner channel with a varying cross section branching off into two arms, one of which arms is provided with a shut-off member capable of isolating the channel from the suction device. In a particular embodiment, the distribution disk is provided with circular perforations arranged along two circular patterns, as well as a set of fins arranged in an alternate sequence with the perforations, which set the seeds in motion in the container and convey them from the release point in the suction device to the point at which they fall into the ground.
In this particular embodiment, as the seeds pass from one ring of perforations to the other there occurs a separation of the seeds which, within certain limits, is independent of the actual size and shape of the seeds. It is, however, quite apparent that the space taken up by the fins arranged in an alternate sequence with the perforations has a limiting effect on the quantity of perforations that can actually be provided in each circular pattern. Consequently, the number of seeds that can be distributed for each rotation of the disk is relatively small.
It therefore ensues that the forward moving speed of the drilling machine in the field is necessarily low so as to obviate any excessively high rotation speed of the disk, which would negatively affect the seeds owing to the centrifugal forces generated. It will be also appreciated that such an arrangement employs quite an expensive and complicated structure.
In another disclosed embodiment, which is adapted to operate in a likewise manner, the distribution disk is not provided with any fins, but is associated with a selector element provided with rectilinear slits. The position of the selector element is adjustable with respect to the perforations of the disk, so that the seeds held by suction in the perforations are caused to impinge the selector element and are in this way separated. However, even such a construction appears to have its drawbacks. As a matter of fact, the circular perforations in the distribution disk cannot be of such a large diameter as to prevent seeds from getting stuck in them or from passing unhindered through them. On the other hand, the perforations cannot have too small a diameter because the suction in the perforations would turn out to be inadequate to effect seed extraction from the hopper. Furthermore, the separator is not efficient when it comes to irregularly shaped seeds or seeds of differing sizes.